A slider typically includes a slider body and a pull tab. The slider body interacts with coupling elements provided on confronting sides of two cooperating tapes to open and close a zipper or slide fastener. When the slider body is moved by pulling the pull-tab, a generally Y-shaped channel located between a top wing and a bottom wing of the slider body meshes together rows of opposing coupling elements of the tapes. When the slider body is moved in the opposite direction, the Y-shaped channel separates the rows of opposing coupling elements.
To prevent the slide fastener from inadvertently opening or closing, some sliders are provided with a locking feature. When the pull-tab is in at least one particular orientation, a locking member engages with the coupling elements of at least one tape, to prevent the slider from moving. When the pull-tab is not in said one particular orientation (for example, is raised so that it is approximately perpendicular to the tapes), the locking member does not engage with the coupling elements of the tapes, and the slider is permitted to move.
Sliders having this type of locking feature are sometimes referred to as “semi-automatic” sliders.
Embodiments of such sliders are disclosed for instance in Patent Document 1 (GB 769 468 A) and Patent Document 2 (US 2012/0260469 A1).
In the slider according to Patent Document 1 (GB 769 468 A) the locking member is a finger integrally formed with the proximal end of the pull-tab. A helical torsion spring is provided, for biasing the pull-tab towards a position approximately parallel with the tapes of the slide fastener, in which said finger prevents the slider from being displaced.
In the slider according to Patent Document 2 (US 2012/0260469 A1) a resilient locking member having a quite complicated shape, preferably made of metal, such as stainless steel, is used. Said resilient locking member is completely exposed in use, and unwanted debris maybe trapped between it and the slider body, with a risk of jamming the operation thereof.